1. Field of the Invention
The present invention relates generally to a relatively simple photopolarimeter and method for measuring the state of polarization of a light beam, and more particularly pertains to a unique and simple photopolarimeter and method for simultaneously measuring all four Stokes parameters defining the state of polarization of a light beam which does not require any of the usual prior art polarizing elements such as wave retarders and polarizers.
2. Discussion of the Prior Art
The most general state of partial polarization of a light beam is conveniently described by the four Stokes parameters (see, for example, M. Born and E. Wolf, Principles of Optics (Pergamon, New York, 1975), p. 554). A large number of photopolarimeters dedicated to the measurement of the Stokes parameters has been introduced, and an excellent review thereof is given by P. S. Hauge, Surface Sci. 96, 108 (1980), and by K. Serkowski, in Planet, Stars and Nebulae Studied with Photopolarimetry (University of Arizona Press, Tucson, 1977), pp.
135-174. Usually the light beam is passed through a sequence of optical elements (analyzing optics that consist of linear retarders, rotators and polarizers), and the emergent light flux is measured by linear photodetection. Flux measurements can be repeated for different (at least four) discrete settings of the analyzing optics, or alternatively, continuous periodic modulation is applied to one or more optical elements and the detected signal is Fourier analyzed to determine the four Stokes parameters (R. M. A. Azzam, Optik 52, 253 (1979)). Other prior art techniques for the simultaneous measurement of all four Stokes parameters employ division of wavefront (E. Collett, Surface Sci. 96, 156 (1980)) and division of amplitude (R. M. A. Azzam, Optica Acta 29, 685 1982)). All of the previously described photopolarimeters require polarizing optical elements such as wave retarders and polarizers.